Looks good Lorna!
WordPress plugins are pretty simple to write aren't they?
A few things worth mentioning:
1. I would suggest using the WordPress HTTP API instead of curl directly. Doing this means that your plugin will also work for people without curl installed. A good tutorial is here: http://planetozh.com/blog/2009/08/how-to-make-http-requests-with-wordpress/
2. It's probably worth mentioning in the readme file that the plugin requires PHP5+. It will help prevent support requests from PHP4 users wondering why the plugin doesn't work.